This book aims to point out the structure of the Ancient Greek 'harmoniai' by a thorough study on their inherent characters ('ethos'). Until now, scholars identified the 'harmoniai' with the Hellenistic concept of 'tonos' that implies a strict definition of form and matter, identity and difference, essence and accident. Nevertheless the history of ideas has shown us that such complex notions were unknown to Presocratic thought; likewise the 'tonoi'. [http://www.olschki.it/libro/9788822251374]